Image Number 13 for United States Patent #8113586.
An apparatus for adjusting the seat back angle, and more particularly an adjuster inclinedly disposed at a lower position of the bottom of the seat back and the rear side of the seat portion, comprising a rotating sleeve, an L-shaped connection body, a large spring, a shift shaft, and a locking device. When the locking device is locked, the seat back is positioned at a desirable inclination angle. When the locking device is unlocked, the shift shaft is axially movable such that the seat back is resiliently supported. Moreover, the compression state of the large spring is adjustable by a to-and-fro rotation of the rotating sleeve. In this way, the operators may adjust the resilience of the seat back 200 according to their own needs for obtaining a greatest sitting comfort.